Modern central processing units (“CPUs”), with increasing processor core frequencies and power densities, are rapidly reaching a point in which the CPU performance is limited by the amount of heat that can be extracted from the CPU by cooling technology.
High performance CPUs sometimes integrate an on-die thermal diode that converts junction temperatures to some electric value. External analog-to-digital (“A/D”) devices can be found on several computer platforms, converting the electric value into usable information for temperature control.
Due to routing and accuracy limitations, the thermal diode is placed in locations which are not at a hotspot of the CPU. A hotspot is a localized region having a higher temperature than regions of the processor adjoining the hotspot. Temperature differences, as high as 15° C. have been observed between the diode location and the hotspot. The result is inaccurate temperature readings and discrepancy between the reported value and the actual temperature used for device specification and control. Inaccurate temperature reading leads to inclusion of higher design margins, increased cooling costs and limited functionality.
Another thermal protection mechanism uses a separate sensor to detect a maximum threshold temperature at the hottest hotspot on the die. Once the threshold is reached, a single trigger occurs and thermal protection is initiated. Other than this single trigger, the sensor provides no other feedback for use in thermal or acoustic management.
If this second sensor is external to the device, the external sensor suffers from time delay and accuracy problems resulting from the physical separation of the sensor from the hotspot.
There is a need for improved on-die temperature monitoring to improve performance in a thermally constrained environment. There is also a need for faster and more accurate reporting, eliminating gaps between thermal measurement and control.